The present invention is directed to hair spray compositions that are applied to the hair to maintain the hair in a predetermined shape or configuration. The compositions impart excellent hair set retention, feel, and washability to sprayed hair. In particular, the present invention relates to aerosol and nonaerosol hair spray compositions comprising a carboxylated polyurethane resin, an organic solvent, and water, wherein the composition preferably is free of a neutralizing agent for the polyurethane resin.
Normal hair can be so fine, limp, and lacking in body that the hair does not hold a hair set well. Furthermore, hair can lose body and be weakened as a result of being subjected to chemically active hair treatments, such as permanent waves and tints. Additionally, hair can be weakened even further by other contributing factors, such as bleaching by the sun or chlorinated swimming pool water.
Hair setting is basically the process of shaping wet hair by the steps of stretching the hair by curling the hair, fixing the hair in place by drying, then combing to give the finishing touches to provide the desired hairstyle. In particular, the setting of wet hair can be accomplished by making flat curls from strands of hair and fixing the curls with hairpins to product xe2x80x9cpin curls.xe2x80x9d Similarly, the wet hair can be set by using any of a variety of rollers or curlers to mechanically fix the hair. In either case, winding of the wet hair is followed by drying, either ambient air drying, electric drying, or hot air, i.e., blow, drying.
The inherent problem encountered in hair setting is the natural tendency of hair to return to its natural shape. For example, set hair returns to its natural shape almost immediately if moistened. Likewise, high humidity conditions accelerate the tendency of hair to return to its natural shape. Therefore, intensive efforts have been directed toward providing a hair set with sufficient holding power to maintain a desired hairstyle until at least the next shampoo, and, therefore, giving the hair set a degree of permanency.
As indicated by the natural tendency of hair to return to its natural shape, hair is an elastic structure. As a result, slight deformations in hair structure resulting from setting the hair are completely reversible. However, the rate of return of hair to its natural shape is dependent upon the method used to deform, or set, the hair. Hair sets performed on wet strands of hair being rolled tightly, either in curls around the finger or on curlers, followed by drying the hair and unrolling the curlers after drying, corresponds to the release of the hair from a deformation-causing load. The deformation, or set, obtained can last for several days, but the set will not be retained if the hair is wetted.
Investigators have sought to delay the combined action of natural forces and moisture that cause hair to return to its original state by applying solutions containing naturally occurring or synthetic polymers after the hair is shaped into a desired configuration. When applied to shaped hair from aqueous or aqueous/alcoholic solutions, the polymers form a film on the hair, after drying, to help maintain the hair in the previously shaped configuration. The polymeric film promotes cohesion and gives stability to the hair set to maintain hold of the set. The principal objective of a setting lotion is to cover the previously styled hair with an invisible polymeric film that gives styled hair a degree of rigidity and protects the hairstyle against wind and humidity.
Hair spray products act in a similar manner. Hair spray products are applied to wet and/or dry hair and contain a polymer, or polymer mixture, that remains fixed on the previously styled hair and effects the hair in various ways. For example, a xe2x80x9cmechanicalxe2x80x9d effect is exerted on each individual hair. The film-forming polymers are used to provide a flexible sheath of polymeric film on the shaped hair after drying, and, therefore, for mechanical reasons, retard the return of each individual hair to its natural shape. In addition, the polymeric film provides an overall stiffening of the hair. The hair behaves as if the individual hair strands are welded together, and the final hairstyle has better cohesion, therefore, resisting the natural forces that return the hair to its natural shape. Finally, the polymeric film protects the hair from humidity. The ability of the polymeric film to attract and absorb water preferably is minimal, such that the polymeric film retards moisture uptake by hair and retards the return of the hair to its natural state.
The general principles of hair setting are thoroughly discussed by C. Zviak, in The Science of Hair Care, Marcel Dekker, pp. 149-181 (1986). Zviak reviews both the polymers used in hair setting products and the formulation principles used to produce a hair set product that provides such beneficial hair set properties as improved hairstyle hold, easy application and combing, quick drying and nonstickiness, good hair body and bounce, increased hair volume and gloss, and hydrophobicity. It is evident that in the formulation of any end-use hairstyling product, some of these benefits must be sacrificed to some degree to achieve a competing benefit. Therefore, the formulation of hair set products has proved difficult.
As a result, to overcome some of the inherent disadvantages of the polymers utilized to set the hair, hair set products are made available in diversified forms in an attempt to minimize the drawbacks of the particular polymer used in the formulation. For example, hair set products are available as plasticizing lotions, plasticizing gels, aerosol foams, all-purpose lotions, hair sprays, holding lotions, conditioners, and shampoos.
Nonionic, cationic, and anionic polymers have been used in hair set products, with the anionic polymers providing the best hair set results. However, anionic polymers also have disadvantages, such as high water solubility, and, therefore, low hydrophobicity, and low substantivity on hair fibers, and, therefore, causing a crust and flaking due to easy elimination from the hair by combing and brushing. As a result, investigators have continued to search for compounds and compositions that provide the primary benefit of improved durability of the hair set.
Therefore, the use of resins, or polymers, in hair sprays is well known, as summarized in Grollier et al. U.S. Pat. No. 4,445,521. The resins typically used in hair sprays are linear vinyl (e.g., an alkyl vinyl ether) or acrylic (e.g., an alkyl acrylate) polymers prepared by copolymerizing two or more monomers in a free radical polymerization reaction. The vinyl and acrylic-based resins are used in relatively high concentrations in a hair spray composition to fix the hair in a particular configuration and to provide good hair set retention. However, at high concentrations, the vinyl and acrylic-based resins exhibit disadvantages that adversely affect the hair, such as poor combing and feel, and excessive stiffness, crust, and flaking.
The vinyl and acrylic-based hair fixative resins typically used in hair sprays were designed for use in anhydrous alcoholic hair spray compositions. The resins, therefore, have excellent compatibility with, and solubility in, alcohols (e.g., ethanol) used in pump spray compositions and hydrocarbons used as propellants in aerosol compositions. However, due to environmental and toxicological concerns, government regulations require a decrease in the amount of organic solvents used in hair spray and related compositions. Therefore, the alcohols and the hydrocarbon gases traditionally present in hair spray compositions are being replaced by water and water-soluble solvents, like dimethyl ether, that pose less harm to the environment.
The solvent changes required by government regulation made the traditional vinyl and acrylic-based resins unsuitable in hair spray compositions. For example, the presence of water in a hair spray composition increases the viscosity of the composition, thereby making spraying difficult to impossible when traditional resins are used. The relatively high viscosity of the compositions, therefore, requires a reduction in the resin concentration of the composition, which, in turn, results in insufficient hair set retention. The presence of water also increases the tackiness of the resin on the hair, thereby prolonging the drying time of the hair spray an the hair. Water also reduces the hair-wetting ability of the compositions, resulting in beading and flaking of the resin from the hair. In the case of aerosol products, the combination of water, resin, and propellant gas results in poor delivery and foaming of the composition, large aerosol particle size, and beading of the resin.
The need to change solvent systems for hair sprays again led investigators to search for new hair setting resins that overcome the disadvantages associated with the vinyl and acrylic resins. As set forth in European Patent Application 0 619 111, one class of resins is the polyurethanes. However, the hair fixative compositions disclosed in EP 0 619 111 require a base to neutralize, and solubilize, the polyurethane resin. It would be desirable to provide an aqueous hair spray composition containing a low amount of volatile organic compounds (VOC), that is free of a base, and that overcomes that disadvantages associated with traditional vinyl and acrylic resins.
The present invention is directed to aerosol and nonaerosol (i.e., pumpable) hair spray compositions containing hydrophilic, carboxylated polyurethane resins. The hair spray compositions impart good hair set retention and natural feel to sprayed hair, and provide superior retention of the hairstyle at high relative humidity. Such results are unexpected because traditional hair fixative resins are hydrophobic. In contrast, the carboxylated polyurethane resins are hydrophilic, yet provide a soft, natural feel to the hair, and the hair is not tacky.
The carboxylated polyurethane resins are soluble in a wide range of water-to-alcohol ratios, without the need to neutralize the resin with a base. Therefore, the hair spray compositions contain a low amount of VOC and are safe to the environment.
In particular, the present invention is directed to hair spray compositions comprising: (a) about 0.25% to about 6%, by total weight of the composition, of a carboxylated polyurethane resin, (b) 0% to about 80%, by total weight of the composition, of an alcohol, like ethanol, and (c) about 15% to about 80%, by total weight of the composition, of water. The hair spray compositions have a pH of about 6 to about 10.
The composition can be applied to the hair as a pump spray. Alternatively, if an aerosol composition is desired, the composition can further comprise about 5% to about 30%, by total weight of the composition, of a propellant. Optional ingredients also can be incorporated into the hair spray composition.
The polyurethane resins, also termed polycarbamyl polyglycols, have pendant carboxyl groups and are hydrophilic. The polyurethane resins have improved tear strength, excellent washability, good adhesion, and are soluble in water and polar solvents, thereby making them useful in hair spray compositions. In addition, the polyurethane resins form clear, low viscosity, solutions in neutral to slightly basic aqueous solvents. Solutions of the hydrophilic polyurethane resins, therefore, are sprayable.
In accordance with an important aspect of the present invention, hair spray compositions exhibit excellent sprayability when the viscosity of a 55% by weight VOC composition is about 1 to about 10 cps or about 1 to about 25 cps for an 80% by weight VOC composition. Compositions having such a viscosity provide a spray particle size of about 20 to about 150 microns.
In accordance with another important aspect of the present invention, the hair spray compositions exhibit improved washability from the hair when the carboxylated polyurethane resin has an acid value of at least 7 mg KOH/g (milligram potassium hydroxide per gram of resin), and preferably about 7 to about 50 mg KOH/g of resin. The polyurethane resins do not require neutralization with a base to provide a useful hair spray composition.
In accordance with one embodiment of the present invention, the carboxylated polyurethane resin used in the hair spray composition is produced by reacting: (a) a diol component comprising a polyoxyalkylene diol; (b) an alkylene glycol; (c) a diisocyanate; (d) water in an amount of about 0.001% to about 0.95% of the combined weight of the reactants; and (e) a 2,2-di(hydroxymethyl)alkanoic acid, preferably 2,2-di(hydroxymethyl)propionic acid, wherein the ratio of NCO (isocyanate) groups to OH (hydroxyl) groups in the water, diol, and glycol mixture, i.e., the R-value, is about 0.4 to about 1.1.
The hydrophilic carboxylated polyurethane resin contains polyoxyalkylene units, i.e., soft segments, and alkylene units, i.e., hard segments, connected through urethane linkages. Also incorporated into the polymer chain is a small amount of diol having a pendant carboxyl group. The polymer chain also contains urea linkages resulting from a reaction between the water and isocyanate groups, which modify the hair styling properties of the polyurethane.
The polyoxyethylene soft segments of the polyurethane resin impart hydrophilicity to the polyurethane. Soft segments derived from polyoxypropylene and polyoxytetramethylene diols provide a softer, but less hydrophilic, polyurethane. Hydrophilic polyurethane resins having improved strength and superior adhesive properties can be formed by using mixtures of polyoxyalkylene diols.
In another embodiment of the present invention, the carboxylated polyurethane resins used in the hair spray composition are produced from (a) a major portion of polyoxyethylene diol having a number molecular weight (Mn) of 6000 to 10,000; (b) an alkylene glycol, preferably diethylene glycol, cyclohexanedimethanol, or dipropylene glycol; (c) a diisocyanate; (d) water in the amount of about 0.01% to about 0.8% by weight; and (e) a 2,2-di-(hydroxymeth-yl)alkanoic acid, wherein the ratio of NCO to OH in the water, diol, and glycol mixture (i.e., the R-value) is about 0.4 to about 0.98. These polyurethane resins are soluble in dilute (neutral to basic) aqueous solutions, and exhibit good sprayability, superior feel, low flaking, desirable crust, and good set retention when applied to hair. The polyurethane resins are hydrophilic, and provide a soft feel in a hydrated state. In a particular embodiment of a polyurethane resin produced with a major portion of polyoxyethylene diol, water is added in the amount of about 0.04% to about 0.25% by weight, and the ratio of NCO to OH of the water, diol and glycol mixture (i.e., the R-value) is about 0.55 to about 0.98 to provide a carboxylated polyurethane resin having improved adhesiveness to the hair and improved slip on the hair, i.e., good combing properties.
Another aspect of the present invention is to provide a hair spray composition that provides good hair set retention at high relative humidity and that imparts a natural feel to the hair. Accordingly, a hydrophilic polyurethane resin incorporated into a present hair spray composition has a weight average molecular weight (Mw) of about 15,000 to about 150,000, and Preferably about 15,000 to about 100,000. The polyurethane resins also have a polydispersibility index (PDI) of about 1 to about 4, and preferably about 1 to about 3. Preferred polyurethane resins have an R-value of about 0.5 to about 1.
In accordance with another important aspect of the present invention, hair spray compositions of the present invention incorporating a carboxylated polyurethane resin having an Mw greater than 30,000 impart a set retention of 62% or higher at 70% and 85% relative humidity. Hair spray compositions incorporating a polyurethane resin having an Mw below 64,000 provide a hair curl compression in the range between 133 to 296 gram force. In addition, hair spray compositions incorporating a carboxylated polyurethane resin having an Mw below 64,000 further improves hair hand feel. A polyurethane resin having an Mw less than 40,000 and R-value less than 0.75 provides sprayed hair having the best feel and the least amount of flaking.